The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore.
(1) Field of the Invention
The present invention relates generally to a method and apparatus for testing electrical equipment, and more particularly to a method and apparatus for testing equipment for tolerance to line-to-line and line-to-ground high voltage spikes.
(2) Description of the Prior Art
Submarine power systems create intermittent high voltage spikes. Submarine equipment electrically connected to such power systems, hereinafter referred to as the xe2x80x9cloadxe2x80x9d, must tolerate these voltage spikes. The high-frequency voltage spikes are classified as line-to-line (i.e., from power line to another power line) or line-to-ground (i.e., running from power line to ground). Each scenario must, be tested to ensure that the load properly tolerates the spikes. Spike tolerance test circuitry includes power frequency blocking circuits that provide low impedance at the higher spike frequencies and limit the power dissipated by the power source through the power frequency blocking circuitry.
To ensure that the load is capable of withstanding the spikes, a spike generator is connected to the equipment under test through power frequency blocking circuitry. Existing power frequency blocking circuitry comprises a RLC circuit with high impedance, or resonance, at the power supply fundamental frequency to limit the power through the line-to-line and line-to-ground connections from the power source; however, this same RLC circuit presents extremely low impedance at the higher, spike frequencies to allow spike conduction to the load.
During submarine equipment spike testing, RLC power frequency blocking circuitry is placed between all power lines and ground. Since submarine power devices are traditionally operated at 400 Hz, the RLC power frequency blocking circuitry provides resonance, or maximum impedance, at the 400 Hz fundamental operational frequency; however, submarine power devices having a 60 Hz fundamental operational frequency are now being utilized. Because the inductor for a RLC power frequency blocking circuit with 60 Hz resonance requires an inductor size approaching a 55-gallon barrel, the typical RLC power frequency blocking circuit cannot be practically implemented for 60 Hz operation. Additionally, such RLC design for 60 Hz operation provides a frequency response with an extremely high Q (ratio of peak (resonant) frequency to half-power bandwidth) that would require unrealistically accurate components to maintain 60 Hz resonance.
There is currently not a practically implemented power frequency blocking circuit for spike testing, with 60 Hz resonance that provides equivalent performance to traditional 400 Hz RLC power frequency blocking circuitry. What is needed is a practically implemented circuit that provides high impedance at 60 Hz, and low impedance at the higher spike frequencies to conduct the voltages from the spike generator to the test equipment, while also protecting the power supply.
It is a general purpose and object of the present invention to provide power frequency blocking circuitry for a system with a 60 Hz power supply operating frequency. It is a further object of the present invention to provide such spike test support using circuit components that are practically implemented. It is yet another object of the present invention to present a circuit with high impedance at 60 Hz, and low impedance at higher frequencies typical of line-to-line and line-to-ground spikes.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
These objects are accomplished with the present invention by a circuit consisting of a parallel combination resistor and capacitor. The circuit provides power line-to-line power frequency blocking for a 60 Hz power supply operating frequency. The power frequency blocking circuit provides an equivalent impedance of 100 ohms from power line to ground at the 60 Hz operating frequency; and, the power frequency blocking circuit equivalent impedance is on the order of 1-2 ohms at frequencies above 1000 Hz where spike conduction is required. The power frequency blocking circuit is placed between each power supply terminal and ground.